For a long time to come, people who enter space will be exposed to high physical risk. They will live in restricted, stimulus impoverished environments, and will have to make do with severely  limited equipment and supplies. They will be cut off from family and friends, and face many challenges within their microsocieties.
Numerous researchers have pursued the hypothesis that isolation and confinement adversely affect psychological and social functioning. The literature reports impaired intellectual functioning; motivational decline; somatic complaints; depression, irritability, and other psychiatric symptoms; and impaired interpersonal relations. These difficulties are not omnipresent in isolated and confined settings, and when they are present, they are not usually severe. However, they must be considered possible and potentially dangerous concomitants of extended spaceflight.
Tomorrow's spaceflight can be expected to pose different challenges to human participants than have previous missions. Judging from Earth-based studies, future missions involving large crews, more spacious environments, and more sophisticated communications with the outside world, might be expected to result in diminution of somatic complaints (Gunderson, 1968), reduction of emotional disturbances (Nardini, Herrmann, and Rasmussen, 1962), and an increase in group harmony and efficiency (Gunderson and Nelson, 1963). On the other hand, large and heterogeneous crews present the opportunity for misunderstandings, value conflicts, clique formation, etc., and long-duration flights can be expected to introduce stresses beyond those experienced in Earth-based studies.
In the chapters that follow we will examine a wide variety of research areas that can contribute to our understanding of the psychological and relational aspects of humans in space. Such an endeavor naturally focuses on identifying problems which could confront the space traveler. This approach should not obscure the likelihood that the space environment contains many of its own psychological and social balancing systems. Nor should this problem orientation be interpreted as a rejection of the role of mankind in space. On the contrary, it is precisely because we believe that the human can adapt to extended spaceflight that we seek to explore the potentially deleterious effects of the space environment and those circumstances which might offset these effects. Efforts to counter any adverse effects of space should not be limited to reinstating conditions of neutrality. If large numbers of people are to spend extended periods of time isolated and confined in space, the goal must be to discover or to establish positive conditions under which psychological functioning and social life can prosper and flourish.
 Until now, space has been a time-limited challenge-something to survive, to master, and to have endured. We are now entering an era when the new astronaut must foresake his short-term approach to space travel and begin to deal with the space environment as a continuing condition. When this occurs, the space traveler will truly begin to live in space.